The GH file in this project has 2 GH python components inside.

1. The first one allows the user to search for a building coordinate by searching for an address

2. The second one allows the user to convert OSM lat and lon degree decimal values to Rhino Points.

1 - Downlaoding OSM Files

This script downloads an OSM file and saves it to drive from a centre point or a search term

Input Varaiable

• search - [string] Search query of the location
• midLat - [float] (optional) latitude of the building
• midLon - [float] (optional) longitude of the building
• bbox - [int] Dimension of one side of bounding box for OSM
• path - [string] A folder directory to save the OSM File
• run - [boolean] A boolean toggle to download the OSM file (Run once)

01 Load Libraries

import xml.etree.ElementTree as ET
import ghpythonlib.treehelpers as th
import math
import urllib2
import json

02 Generate an API Key from positionstack

www.positionstack.com

KEY = 'YOUR API KEY HERE'

Create option to either search or use manual midLat and midLon

if search:
    print 'Search Tag found' 
    query = search.replace(" ", "%20")
    url = 'http://api.positionstack.com/v1/forward?access_key='+KEY+'&query='+query
    response = urllib2.urlopen(url)
    data = json.load(response)   
    midLon = data['data'][0]['longitude']
    midLat = data['data'][0]['latitude']
else:
    print 'Search Tag not Found. Enter search term or use midLat and midLon'

Constants for calculating the bounding box

R = 6371000

03 Bounding Box calculation

#111110 is the distance of 1 degree in meters for the Y direction (Latitude) #X distance per degree = [cosine(latitude)*Y distance in radians] #bbox here is the dimension of the boundarybox side

dY = (bbox/2) / 111110
dX = dY / math.cos(math.radians(midLat))

Calculation the extents of the bounding box

a = str(midLon - dX)
b = str(midLat - dY)
c = str(midLon + dX)
d = str(midLat + dY)
bbox = a +','+ b + ',' + c + ',' + d

04 Requesting OSM file from OverpassAPI

url = 'https://overpass-api.de/api/map?bbox='+bbox
if run:
    response = urllib2.urlopen(url)
    filePath = path+'file.osm'
    mydata = response.read()
    file = open(filePath, "w")
    file.write(mydata)
    file.close()
else:
    filePath = path+'file.osm'

2 - OSM to Points

This example is to demonstrate how decimal degree coordinates can be translated to cartesian points

Load Libraries

import rhinoscriptsyntax as rs
import xml.etree.ElementTree as ET
import ghpythonlib.treehelpers as th
import math

Setup Constants

R = 6371000

Parse Lat Lon

lat = []
lon = []
tree = ET.parse(filePath)
root = tree.getroot()
for element in root.findall('node'):
    lat.append(float(element.get('lat')))
    lon.append(float(element.get('lon')))

Parse Bounds

for element in root.findall('bounds'):
    minlat = float(element.get('minlat'))
    minlon = float(element.get('minlon'))
    maxlat = float(element.get('maxlat'))
    maxlon = float(element.get('maxlon'))

Find midpoint (Centre of Bounding Box)

midlat = (minlat+maxlat)/2
midlon = (minlon+maxlon)/2

Calculate distance per degree

Math behind the code

The Longitude distance per degree is along the x-axis remains constant around the circumference of the earth The Latitude distance per degree however, varies. It is largest by the equator and shorter towards the pole since the Latitude lines are parallel to oneanother.

Y Distance

(2 * pi * R) Radian Distance = 360 degrees

Y Distance per degree = (pi * R) / 180 (Where R is the radius of the earth in meters - 6371000m)

X Distance

X Distance per degree = cosine(Latitude) * Y Distance per degree

ydistperdegree = (math.pi*R)/180
xdistperdegree = ((math.cos(midlat*(math.pi/180))*R)*(math.pi/180))

Calculate x and y component of points

x_comp = []
y_comp = []
for i in lon:
    x_comp.append((i-minlon)*xdistperdegree)
for i in lat:
    y_comp.append((i-minlat)*ydistperdegree)
Points = []
for i in range(len(x_comp)):
    Points.append(rs.CreatePoint(x_comp[i],y_comp[i],0))

Create boundary rectangle

plane = rs.WorldXYPlane()
Boundary = rs.AddRectangle(plane,((maxlon-minlon)*xdistperdegree),((maxlat-minlat)*ydistperdegree))